A spark plug includes an outer shell and an insulator core. A ground electrode extends from the outer shell and a firing center electrode extends from the insulator core. The electrodes together define a spark plug gap. When the spark plug is installed and operated in the combustion chamber of an engine, a spark is formed in the spark plug gap. The spark ignites a mixture of fuel and air in the combustion chamber.
The quality of the spark affects the ignition of the mixture of fuel and air. The quality of the spark is determined by factors such as the condition of the spark plug gap, the voltage applied across the spark plug gap, and the material composition of the electrodes. A spark plug electrode made of a precious metal such as platinum provides a high quality spark. Platinum and other precious metals, however, are expensive, which limits their use in spark plug electrodes or increases the price of the resulting spark plug.